duplicates in net functions

[Matthieu Patou]

Hello jelmer,

Following your integration of the python implementation of some net 
function it comes clear to me that some functions are duplicated.

ie. net user add and net newuser or net password and net setpassword

Also it might be interesting to consolidate functions, ie net setexpiry 
can be merged in net user setexpiry. The same maybe for net enableaccount.

Matthieu.